title: Maximising retention in a longitudinal study of genital Chlamydia trachomatis among young women in Australia.
abstract: BACKGROUND
  Cohort studies are an important study design however they are difficult to implement, often suffer from poor retention, low participation and bias. The aims of this paper are to describe the methods used to recruit and retain young women in a longitudinal study and to explore factors associated with loss to follow up.
  
  
  METHODS
  The Chlamydia Incidence and Re-infection Rates Study (CIRIS) was a longitudinal study of Australian women aged 16 to 25 years recruited from primary health care clinics. They were followed up via the post at three-monthly intervals and required to return questionnaires and self collected vaginal swabs for chlamydia testing. The protocol was designed to maximise retention in the study and included using recruiting staff independent of the clinic staff, recruiting in private, regular communication with study staff, making the follow up as straightforward as possible and providing incentives and small gifts to engender good will.
  
  
  RESULTS
  The study recruited 66% of eligible women. Despite the nature of the study (sexual health) and the mobility of the women (35% moved address at least once), 79% of the women completed the final stage of the study after 12 months. Loss to follow up bias was associated with lower education level [adjusted hazard ratio (AHR): 0.7 (95% Confidence Interval (CI): 0.5, 1.0)], recruitment from a sexual health centre as opposed to a general practice clinic [AHR: 1.6 (95% CI: 1.0, 2.7)] and previously testing positive for chlamydia [AHR: 0.8 (95% CI: 0.5, 1.0)]. No other factors such as age, numbers of sexual partners were associated with loss to follow up.
  
  
  CONCLUSIONS
  The methods used were considered effective for recruiting and retaining women in the study. Further research is needed to improve participation from less well-educated women.
authors.affiliation: Centre for Women's Health, Gender and Society, School of Population Health, University of Melbourne, Victoria 3010, Australia. walker@unimelb.edu.au
authors.forename: Jennifer
authors.initials: J
authors.lastname: Walker
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Fairley
authors.forename: Eve
authors.initials: E
authors.lastname: Urban
authors.forename: Marcus Y
authors.initials: MY
authors.lastname: Chen
authors.forename: Catriona
authors.initials: C
authors.lastname: Bradshaw
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Walker
authors.forename: Basil
authors.initials: B
authors.lastname: Donovan
authors.forename: Sepehr N
authors.initials: SN
authors.lastname: Tabrizi
authors.forename: Kathleen
authors.initials: K
authors.lastname: McNamee
authors.forename: Marian
authors.initials: M
authors.lastname: Currie
authors.forename: Marie
authors.initials: M
authors.lastname: Pirotta
authors.forename: John
authors.initials: J
authors.lastname: Kaldor
authors.forename: Lyle C
authors.initials: LC
authors.lastname: Gurrin
authors.forename: Hudson
authors.initials: H
authors.lastname: Birden
authors.forename: Veerakathy
authors.initials: V
authors.lastname: Harindra
authors.forename: Francis J
authors.initials: FJ
authors.lastname: Bowden
authors.forename: Suzanne
authors.initials: S
authors.lastname: Garland
authors.forename: Jane M
authors.initials: JM
authors.lastname: Gunn
authors.forename: Jane S
authors.initials: JS
authors.lastname: Hocking
mesh_terms: D000293:Adolescent; D000328:Adult; D001315:Australia / Q000453:epidemiology; D002690:Chlamydia Infections / Q000453:epidemiology* / Q000517:prevention & control; D002692:Chlamydia trachomatis / Q000302:isolation & purification*; D015331:Cohort Studies; D005260:Female; D005831:Genital Diseases, Female / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D010352:Patient Dropouts; D018579:Patient Selection; D011446:Prospective Studies; D012008:Recurrence; D055815:Young Adult